Aluminum modified water absorbent composition

Abstract

The present invention describes a composition useful for absorbing substantial quantities of water and a preferred process for the manufacture of such compositions.

What is claimed is: 
     
       1. A hydrolyzed starch graft copolymer having in its anionic form carboxyl and amide functionality wherein a substantial portion of the anionic form of the hydroxyzed starch graft copolymer is uniformly reacted to form the aluminum salt said aluminum salt being formed prior to the drying of the hydrolyzed starch graft copolymer wherein from about 5 percent to about 95 percent by weight of the free carboxyl groups present are neutralized with aluminum. 
     
     
       2. The hydrolyzed starch graft copolymer of claim 1 wherein from about 10% to about 75% by weight of free carboxyl groups are neutralized with aluminum. 
     
     
       3. A process for preparing a compound according to claim 1 wherein the aluminum salt is formed during alkaline hydrolysis of the acrylonitrile starch graft copolymer. 
     
     
       4. The process of claim 3 wherein the basic form of aluminum is employed during hydrolysis. 
     
     
       5. The process of claim 3 wherein the basic form of aluminum is aluminum hydroxide. 
     
     
       6. The process of claim 3 wherein the excess base is washed out of the starch graft copolymer with an alcohol. 
     
     
       7. The process of claim 3 wherein the aluminum salt is formed subsequent to hydrolysis. 
     
     
       8. A process according to claim 3 wherein the hydrolyzed starch graft copolymer is surface treated in a subsequent step to form a product having a linkage density at the particle surface greater than the linkage density in the particle interior.